


Promises to my valentine

by Animillion



Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Dry Humping, Father/Son Incest, Incest, LotsOfLoveEvent - Celebrating Valentines Day, LotsOfLoveEvent - Fluff, M/M, Obsessive!Senku, Promises, Senku cums fast cause he can’t help it, TKSLotsOfLoveFeb2020, TKSevents, TheKingdomofShipping, age gap, make out, thigh fucking
Language: English
Status: Completed
Published: 2020-02-09
Updated: 2020-02-09
Packaged: 2021-02-27 20:01:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,402
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22611433
Author URL: https://archiveofourown.org/users/Animillion/pseuds/Animillion
Summary: Senku will remember things for years if he’s passionate enough about it. And he refuses to forget the promise Byakuya made to him on Valentine’s Day, 6 years ago. This year, he is going to make Byakuya his Valentine for sure.
Relationships: Ishigami Byakuya/Ishigami Senkuu
Comments: 4
Kudos: 47
Collections: TKS Lots of Love/Valentines and RP Month - February 2020





	Promises to my valentine

“Be my Valentine.” Senku holds up a card with red and pink hearts glued with stick glue out to Byakuya. Young and naive and oh so adorable, little Senku was. 

His father looks at him with utter shock. He laughs into the back of his hand. That’s right. For the past few years Senku hasn’t gotten any valentine cards in his mailbox at school. Well, aside from his teachers of course and probably Taiju’s. 

Valentine’s Day wasn’t something the professor really concerned himself too much with. It was a day for lovers and young things to blossom. And perhaps in some cases there would be more love to give nine months later. But Byakuya was a single parent running on caffeine half of the time. The most love he has is for his son. His son who is looking so adamantly up at him with this card. A little pout on his face. He had about a year and a half before hitting his teens and Byakuya knew he was much more mature than something like this. Still, it swells his heart to take the card from him. 

“Oh? You have something for me for valentines Senku?” He laughs and opens it up. There’s a drawing of them inside. Senku is very good at drawing. It’s from all of the make shift blue prints he’s made over the years. 

“Didn’t I just tell you to be my valentine?” The boy crosses his arms. 

Byakuya laughs into his hand again as his eyes scan the card’s words fondly. 

_Byakuya, I love you, so be mine._

It was very straight forward. So much so that he knew Senku came up with it all on his own of course. He ruffles the boys hair with a smile. 

“Of course, I love you too Senku~” he chimes, heart absolutely bursting. 

“Not just family love either, that’s not what I meant.” Senku crosses his arms, “are you sure you love me then?”

Byakuya is taken aback and looks back down to the letter then to his mischief maker. “I think you’re confused Senku, you can’t love me more than family because uhh,” he thinks a little hard to try and escape the situation. This feels like when his students get crushes on him. “You can’t love me that way, you’re not an adult yet so you don’t understand.”

Senku’s brows twitch in anger and he huffs. “I knew you’d say something like that old man.” He snatched the card back from him. “Fine! But when I am an adult you have to say yes to being my valentine Byakuya.” The man smiles at him, ruffling his hair again. 

“Okay okay I promise.” He coos before kissing his forehead. 

“I won’t forget.”

“Oh I’m sure.” 

“I really won’t, so you better not.” 

“For sure I won’t.” 

-

Byakuya forgot. He totally forgot about it, in fact. Because the next year Senku didn’t even mention what he had proposed on the year before. He had no reason to worry about it. He just thought the little crush his adopted son had had flew away with as he got older. 

Byakuya never expected, February 14 at 12 am Senku would barge into his room to wake him up. The man sits up on his futon, wincing at the light Senku turned on. 

“Senku? What are you doing? It’s the middle of the night.” He yawns. 

“It’s now officially 41 days since my eighteenth birthday.” He crosses his arms and looks at Byakuya expectantly. 

He looks up at the green haired teen in wonder. What could he possibly mean by such a statement? Was there something Byakuya had forgotten? Senku’s birthday had been absolutely wonderful. His young man growing up so fast made Byakuya want to cry a little. 

“It’s Valentine’s Day, you remember don’t you? Hah, I wouldn’t be surprised if an old man like you has forgotten.” Senku crosses his arms. 

Byakuya squints in hard thought. Valentine’s Day was 41 days from Senku’s birthday. That was special because... he’s 18? Senku pulls out a card from his pajama pants pocket. It was crumpled and old and has creases where it’s been folded and smoothed out. The hearts glued on it curl because they’re peeling but it’s obvious they were stuck by super glue now. 

The card has everything clicking in Byakuya’s head. Had Senku really kept that all these years because of him? Senku hands it out to him and looks at it. His heart was filling with something indescribable. “Senku...” He doesn’t want to hurt his boy. Doesn’t want to break his heart. But he can’t find the words to even do that when he looks up at him. 

“You promised to be my valentine, Byakuya.” 

“Yes, I did.” 

The teens eyes light up at this and a slow smile grows on his face. He takes this as his cue and without a word, he pushes Byakuya back on the futon. The man makes a light ‘omph’ noise and looks up at his son who’s now straddling him and looking unbelievably overjoyed. 

“Senku, you can’t be serious though- I’m your father-“

“No!” Byakuya pauses, shocked as Senku takes both of his hands on either side of Byakuya’s face to caress him. “You’re so much more than that to me, Byakuya... you always have been, that’s why I wanted you to accept my feelings all those years ago... you waved me off like my feelings would go away but I believed you when you promised to be mine on the year of my eighteenth birthday, when I finally become an adult.” Senku speaks from the heart. 

Byakuya was scared. This wasn’t right. Was this his son? He holds Senku’s face just the same as he’s doing to him. “Are you feeling well Senku? You’re acting so different, so strange, I’m worried.”

“I’ve been holding back for years Byakuya,” Senku pouts. His pupils may as well have been shaped like hearts. 

The older man is afraid for his son. His own heart is beating a quick over his thoughts. Byakuya had never tried to look at him this way. Senku was his incredibly curious and smart son. If there was a problem, Senku could solve it. His rocket parts littered the apartment complexes yard and weaves into the grass from how many experiments he’s fiddled with out there. Senku has a mouth on him, but he’s never truly ill willed towards anyone. 

An old rough thumb pets along the cheek it holds without thinking. There’s no way he’s ever _tried_ to think about Senku this way. But now Senku is forcing him to acknowledge the thought. To toy and entertain it. 

“My feelings since back then haven’t changed, I’ve been waiting for so long for you to accept me so...” Byakuya knew he wasn’t going to beg him. The teen knew if he begged Byakuya was sure to give in regardless of his true feelings. “Have yours changed?”

Yes. Ten billion times yes they have. Without him even realizing it too. In the past he’s sure if Senku had pinned him to his futon in the middle of the night he would immediately shove him off and away. Senku was weak, and even now he would be able to push him away. But he hasn’t yet. He’s stayed put and stared in awe as if he’d been told something unbelievable. And quite frankly he has. 

“Yes,” he swallows thickly and his eyes dare to travel down further along Senku’s body clothed by a cute button up night shirt. He doesn’t want his feelings to change. They already have. Senku looks happy again. 

“Say it, Byakuya, say you’ll be mine.” It’s demanding and quite like him to sound this way. 

Instead of saying anything though, Byakuya pulls Senku down. Their lips meet and soon they form a kiss. Senku’s breath presses hard against the mans skin and he can’t help but want to kiss him again. Their lips slide past each other passionately, methodically, daring to test the boundaries of right and wrong. 

The card falls somewhere on the futon when Senku lets it go to put a hand in Byakuya’s hair, not wanting the kiss to end. 

They breath hard against each other. Provoking him further, Senku presses his now hard and clothed erection against Byakuya’s own. 

The man moans into his lips. He puts his hands on the younger’s hips to guide him to only straddle one of his thighs, pressing it feverishly into the outline of his dick. Senku gasps and rocks his hips on his thigh for stimulation. 

Byakuya was the most intrigued he’d ever been. Senku was rocking his hips so wantonly on him, moaning into their unbreakable kiss. 

“Senku,” he whispers against plush pink lips only getting a breathy moan in reply. “It’s okay, you don’t have to hold back any longer, I accept you.” 

He hopes Senku accepts him as well. Accepts his hands slipping under his night shirt and up his body. To those perky pink nipples dying to be toyed with. He hopes he accepts the attention he gives his neck, licking and biting the tantalizingly sweet skin. 

The teen is a mess, following his carnal desires as Byakuya messes with him. Basking in the ethereal pleasure he gets from all of the attention he’s finally getting. The attention he has been dreaming of for six years. It finally was coming to fruition. 

“You’re a mess Senku, you make me a mess, look what you’ve done.” Byakuya chuckles half heartedly into his ear. 

“Byakuya,” he moans loud and unashamed into the air as his hips jerk rapid against the man’s thigh. “I’m gonna cum.” He’s whimpering, forehead settling into Byakuya’s neck. 

“Go ahead,” he presses his thigh up into his rapid grinding. 

Senku moans and shakes, fingers clenching and unclenching in Byakuya’s hair. His cock twitches against the mans thigh and he continues thrusting his hips against him until he can no longer stand the stimulation. 

Senku enjoys the praise he gets in the after glow. His hair is pet and kisses are made on his face. Byakuya holds him close, making him hum in happiness. 

“I want you to feel good, since I’m yours you can do whatever you want to me you know.” Senku teases him, leaning up and grinning at the other, hoping for something interesting. 

Byakuya laughs, “you want to tempt me that far, my valentine?” He pushes at Senku’s bottoms and the teen is quick to shimmy them off. They’re covering in his cum, as is his lower half and it causes a large blush to bloom over his face. Byakuya guides him to move upwards and in between him now. The man has his own erection out and grins when Senku realized what he was doing. 

His cock slides between milky white thighs and he watches every bit of confidence drain from the teen. 

“You’ve thought of this before, haven’t you? Perv..” Senku can’t believe the man was slowly gyrating his hips to use his thighs for stimulation. It feels weird, but it nonetheless was turning him on again. And Byakuya is bigger than he had imagined. He was definitely what one would refer to as a grower. It’s thick and hot and Senku can’t help but to moan as if it was actually inside him. He wants it inside him. 

“Senku you-“ he grunts “-have no idea how much I never wanted to do this.” 

The teen looks at him, squeezing his thighs together in response. Byakuya moans, hips pushing upwards into them much faster. The stimulate crosses Senku’s balls every so often, sending a shudder through his spine. 

“You don’t have to hold yourself back anymore Byakuya, I’ll accept you no matter what.” He reassures, pressing feverish kisses where he could to the man’s face. 

He grunts at this, forcefully pushing Senku down to help him along. Senku’s cock is being rubbed between them and he can’t help but to whimper at the feel good sting. 

“Mark me as yours Byakuya, it’s so obvious you want to as much as I want it.” He dips in for another kiss. It was an odd position to thigh fuck in, but the man was going to make it work nonetheless. 

The sliding and lubrications from his precum cause lewd slapping noises to sound through the room. Byakuya had never wanted to do this to his son. Never wanted to defile him in such a way. But now it was Valentine’s Day, and Senku was eighteen, and as fucked up as it was he had waited for this for years and years. His chest swells with love for him. Senku was so patient. He had really taken his words to heart that day. A part of him is grateful that he had. 

He can’t believe he’s touching him this way now. He squeezed Senku’s hips and nipped at his neck. He gets to feel that smooth skin and pudgy stomach rubbing against him. 

“I’m gonna make you mine,” he says, eyes dilating as their matching crimson eyes meet. 

“Yes, please, that’s what I want.” Senku seems to have those heart pupils again. It hurts to know how obsessed he was. But he loves him too much to want him to stop. The heat is building within the man and soon he’s spilling out all over the back and in between Senku’s thighs. He uses the stimulation until every last drop is stained into the milky white skin. The stained teen moans, pressing his body close to Byakuya’s. “Yes~” he says triumphantly. 

Panting is the only thing moving either of them. Senku nuzzles against Byakuya’s shoulder. 

“I’ll be your valentine for as long as you want.” It’s barely a whisper yet hardly aloud. 

“Now this is exciting,” Senku lifts and their lips meet again. 

The card is on the floor now, open. It’s the same picture as before. Byakuya didn’t even look at the card again before Senku had started in head first. The old words were erased out. As was years and years of writing letters and erasing them. The fade of the eraser letters can be seen behind the marker note over lapping them. 

_I want you to be mine, I want you to make me yours and only yours. Byakuya, I am a sick perverted son, but these are my feelings. Be my valentine, be mine._

**Author's Note:**

> >w< I wanted to make this longer but I ended up running out of words :p /if I worked on it anymore I was going to end up feeling like it’s trash 
> 
> I hope you enjoyed this adorableness! Byakuya, in the end, can never hide his true feelings after Senku admits his own. Senku is adamant, and Byakuya is WEAK for him ❤️


End file.
